1. Technical Field
The present invention relates to a monofocal optical lens system. More in particularly, the present invention relates to a compact monofocal optical lens system applicable to electronic products.
2. Description of Related Art
In recent years, with the popularity of mobile products with camera functionalities, the demand of miniaturized optical lens systems is increasing. The sensor of a conventional photographing camera is typically a CCD (Charge-Coupled Device) or a CMOS (Complementary Metal-Oxide-Semiconductor) sensor. As the advanced semiconductor manufacturing technologies have allowed the pixel size of sensors to be reduced and compact optical lens systems have gradually evolved toward the field of higher megapixels, there is an increasing demand for compact optical lens systems featuring better image quality.
A conventional compact optical lens system employed in a portable electronic product mainly adopts a four-element lens structure such as the one disclosed in U.S. Pat. No. 7,869,142. Due to the popularity of mobile products with high-end specifications, such as smart phones and PDAs (Personal Digital Assistants), the requirements for high resolution and image quality of modern compact optical lens systems increases significantly. However, the conventional four-element lens structure cannot satisfy these requirements of the compact optical lens system.
Other conventional compact optical lens systems with five-element lens structure such as the ones disclosed in U.S. Pat. Nos. 8,000,030 and 8,000,031 enhance image quality and resolving power. However, the shape of the image-side surface of the fifth lens element cannot reduce the angle at which the incident light projects onto the image sensor. Therefore, the photosensitivity of the image sensor cannot be increased, and the image quality of the optical lens system cannot be retained.